Way to not cause a scroll bar when using a non-Google Calendar iFrame in the new Toolkit Helpers?

Hello, I know I am going a little outside the toolkit helper's purpose, but I am using it to embed a form from my client support into the page.

It does work: http://test.saviodesigns.com/sd2019/iframe.php
however, it is adding an interior scroll bar instead of basically letting the page grow vertically to fit the form. I know this is likely an issue with using the iframe, but I was hoping there was/is a way to prevent that from happening so that it has a seamless look?

I have tried a couple internet suggestions, but they don't quite seem to work - they seemed to be for older types of code/design.